1. Field
One or more embodiments of the present disclosure relate to a light-emitting diode (LED) light fixture, and more particularly, to an LED light fixture with a channel-type heat dissipation system including a plurality of light-emitting devices including LEDs, a heat dissipation unit connected with the light-emitting devices and having the light-emitting devices mounted thereon, a casing accommodating the heat dissipation unit and the light-emitting devices, a cover connected with the casing, disposed above the light-emitting devices, and that is light-transmissive, and a ventilation channel through which ambient air passes, in which the casing has one open surface, the cover is connected to cover the open surface, the heat dissipation unit has an upper surface exposed through the open surface and a lower surface, the light-emitting devices are connected to the upper surface of the heat dissipation unit and exposed through the open surface, the heat dissipation unit includes a plurality of ridge portions extending in at least one direction and furrow portions formed between the ridge portions, the casing includes a plurality of vent holes, and the ventilation channel includes air flow paths formed by the furrow portions and the vent holes formed in the casing.
2. Description of the Related Art
An LED is a light-emitting device that generates light when electrons and holes combine in an active layer. Although an LED is environmentally friendly and consumes low power, the LED generates light of high brightness and thus is attracting attention as a next-generation light-emitting device. Accordingly, light-emitting devices employing LEDs are widely being developed and used and also use of LEDs is being recommended and supported in many ways nationally.
As flat panel display devices, flexible devices, LEDs, packages for vehicles, small electronic devices, and information and communication devices become slim and integrated, a countermeasure against heat is at issue. In particular, light fixtures employing LEDs have high illumination intensity in spite of low energy consumption and may be used for a long time due to a long lifespan. Also, light fixtures employing LEDs do not require mercury for light emission. In other words, light fixtures employing LEDs are environmentally friendly, and thus, are under development in many ways to replace incandescent lamps, fluorescent lamps, and metal halide lamps that have high energy consumptions and short lifespans. Such an LED device is a photoelectric device, has a junction of p-type and n-type semiconductors, and is a light source that emits energy corresponding to the band gap of the semiconductor in the form of light due to the combination of electrons and holes when a voltage is applied. Recently, LEDs of various colors, including blue, have been developed and are being applied to various usages, such as large outdoor electronic displays, traffic lights, car instrument panels, and street lights, because it is possible to display natural colors.
An LED as a white light source emits only about 15% to about 25% of its total heat energy as radiant energy and emits all the other heat energy behind its heat source by conduction and convection, unlike a fluorescent lamp, an incandescent lamp, or a metal halide lamp that has a high efficiency in converting electric power into light, but directly emits about 58% to about 81% of its total heat energy as radiant energy. Since the emitted heat has direct effects on semiconductor devices around a light-emitting unit, the LED as a white light source is very vulnerable to heat, compared to a light-emitting device, such as an incandescent lamp employing a filament or a fluorescent lamp employing cathode rays. Therefore, in order to apply a large amount of current to an LED, a heat dissipation structure for efficiently emitting heat generated from the LED to the ambient air by conduction and convection becomes a very important element.
Problems caused by overheating of an LED light source include the degradation of optical power resulting from a change in the refractive index of an LED encapsulant, thermal deformation at a bimaterial interface, a reduction in the lifespan of an LED resulting from discoloration, the performance degradation of a fluorescent body resulting from die break and stripping, and so on. In order to prevent such degradation of an LED light source, a variety of heat dissipation countermeasures are being attempted. As a typical heat dissipation countermeasure, thermal interface materials (TIMs) capable of reducing a contact thermal resistance and heat sinks having heat dissipation fins of various forms are in use. TIMs are intended to reduce contact thermal resistance between an LED package and a printed circuit board (PCB) substrate, or between a PCB and a heat sink, and used as thermally conductive materials in the form of paste, grease, and tape. However, first of all, it is necessary to design the optimal structure of a heat dissipation system, such as a heat sink, that is most important for the improvement of heat dissipation characteristics.
Heat sinks are mainly used in the form of heat dissipation fins or pins, that is, in a plate shape or a pin shape. Although there are a variety of forms of heat sinks, the heat sinks are inserted in outer cases designed to protect an external design, electronic parts, a circuit package, modules, and so on. For example, in the case of an LED light fixture having high output power in which LED light sources are arranged in a columnar array structure or in a multiple array structure, such as a street light, high heat is generated, and thus a heat sink in which as many pin-shaped or plate-shaped heat dissipation fins as possible are arranged to have a large area is used. However, due to a limitation on the internal space of a light fixture and regulations on the weight, it is necessary to design a heat sink to be as compact as possible according to the space of the fixture and also as light as possible. For this reason, it is difficult to improve heat dissipation characteristics.